"Wario placed third in the poll, but with Bowser and Peach pencilled in, Sakurai didn't want to include 3 Mario newcomers."

but this was in 2002, you say. perhaps he changed his mind since?

well, look at brawl in 2008. you can see how mario was limited to four slots, and there was no new mario character in general.

my point is, it seems like sakurai wants to keep slots for each series four at the very maximum. yes, i know dr. mario was the 5th mario rep, but he was just there to fill a slot pretty much, considering melee was a very rushed game. and as mentioned in the notes above, sakurai did consider wario to be a mario clone, but felt like he deserved better.

with that very lone exception, no series has gone beyond four slots. maybe in total characters with transformations, but never above four slots, and i think it should stay that way.---wargle gargle

Wario was treated as part of his own series in Brawl, so I see no reason why Waluigi wouldn't go that Wario's series as well.---Though our government may be tight-fisted,Its citizens are rather TWSSted.